1. Whiteboard Protocol Bell Work: What is the formula for acceleration?
Objective: TLW how to calculate Kinetic and Potential energy.
Classwork: beauregardchemistry.weebly.com/.../kinetic_and_potential_energy_ worksheet.docx ‎
Homework: Physics Book page 172; Practice D
Exit ticket: What is the PE of a car with a mass of 50 kg and sitting on a hill that is 4 m tall?
7/20/2019

2. ENERGY
The Ability to do Work

3. Energy can be defined as the ability to do work
7/20/2019

4. Energy There are many forms of energy Potential Energy Kinetic Energy
Electrical Energy
Mechanical Energy
Gravitational Energy
Chemical Energy
7/20/2019

5. POTENTIAL ENERGY Potential energy can be defined as energy at rest.
Example:
A pencil sitting on an edge of a desk
A ball sitting still on the floor
A rubber band stretched-out
7/20/2019

6. PE = MGH Potential Energy The formula for potential Energy is:
7/20/2019

7. Potential Energy Where: PE = Potential Energy M = Mass
G = Gravitational Constant
(  9.8 m/s2)
H = Height
7/20/2019

8. Potential Energy
The formula for Potential Energy can be used to calculated the amount of energy used.
Example:
What is the Potential energy of a rubber ball that has a mass of 50 kg and is rolling down an incline that is 4 m high?
7/20/2019

9. Potential Energy The formulas for Potential Energy are as follows:
PE = mgh ( Potential Energy)
M = PE/gh ( Mass)
H = PE/ mg (Height)
7/20/2019

10. Potential Energy
The first step is to determine what has been given in the problem.
PE = ?
M = 50 kg
G = 9.8 m/s2
H = 4 m
7/20/2019

11. Potential Energy = (50kg) (9.8 m/s) ( 4m) = 1962 J PE = MGH 7/20/2019

12. Potential Energy Example 2:
Calculate the mass of a flying bird that is flying 8 m above the ground with a PE of 100 J.
7/20/2019

13. Potential Energy PE = 100 J H = 8 m G = 9.81 m/s M = ?
What do we know?
PE = 100 J
H = 8 m
G = 9.81 m/s
M = ?
7/20/2019

14. M = PE/GH = 100 J / (9.81) (8 m) = 100 J / 78.48 = 1.27 kg
Potential Energy
M = PE/GH = 100 J / (9.81) (8 m) = 100 J / = 1.27 kg
7/20/2019

15. Potential Energy
Example 3:
How high off the ground a bird is flying if its mass is 10 kg and it has a PE of 30 J?
7/20/2019

16. Potential Energy What do we know? PE = 30 J M = 10 kg H = ? G = 9.81
7/20/2019

17. Potential Energy
H = PE / MG = 30 J/(10kg) (9.81 m/s) = 30 J / 98.1 = .31 m
7/20/2019

18. Summative Assessment
Complete the following quiz found at this website:
7/20/2019